Plasma is the liquid component of blood in which blood cells are normally suspended. Serum is that portion of plasma in which clotting factors such as fibrinogens have been removed. Plasma (including serum) forms about 55% of the total volume of blood. It is mostly water (about 92-93% by volume) and contains dissolved proteins, glucose, clotting factors, mineral ions, hormones and carbon dioxide. While plasma may be prepared by spinning a tube of fresh blood containing an anti-coagulant in a centrifuge until the blood cells fall to the bottom of the tube, other techniques for producing plasma are still needed. Plasma or serum may be important, for instance, for testing or diagnostics, e.g., for infections, diabetes (e.g., sugar), AIDS (e.g., HIV), cancer (e.g., prostate-specific antigen), or other indications. In many cases, only a relatively small amount of plasma or serum is needed for testing purposes; however, a much large volume of blood is often required for centrifugation and/or processing.